补偿网络对Cascode结构放大器线性度的改善  

Improvement of linearity in Cascode broadband amplifier by resistance-inductance-capacitance compensation network

作　　者：张晓东[1] 王钟[1] 高怀 程建春[1] 吴浩东[1] 

机构地区：[1]近代声学教育部重点实验室,南京大学声学研究所,南京210093 [2]苏州市射频功率器件及电路工程技术研究中心,苏州215123

出　　处：《南京大学学报（自然科学版）》2012年第5期671-676,共6页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金(11174143);江苏省科技支撑计划--工业部分(BE2010006)

摘　　要：宽带功率放大器是现代多频段无线通信系统中的关键器件.Cascode结构由于其良好的带宽特性以及输出阻抗特性,被广泛应用在宽带功率放大器的设计当中.带宽和线性是宽带功率放大器的重要指标.通常用RLC补偿网络可以增加Cascode结构功率放大器的带宽.本文提出通过选择合适的RLC补偿网络电路参数,使得晶体管处于良好的工作状态,可以实现在增加Cascode放大器带宽的同时,改善其线性度.从电路原理上分析了——补偿网络改善功率放大器非线性的原因,并利用Volterra级数方法计算了三阶交调截止点(IP3),证实了IP3可以改善3dB±.采用2μm InGaP/GaAs HBT半导体工艺流片后,测试结果表明,其3dB工作宽带扩展了1GHz(带宽从1.5GHz扩展到2.5GHz),IP3改善了3dB,与计算结果非常一致.With the development of wireless communication,the system needs to cover multiple frequency bands for different standard;therefore broadband power amplifiers will play a more and more important role in multi-band power amplifier modules（PAMs）.The cascode structure,composed of a common-emitter（CE） and a common-base（CB） transistor,is widely used in the broadband power amplifier design because of its miller effect capacitance suppression and high output impedance.RLC peaking technology is a well-known approach to broaden the bandwidth of cascode power amplifiers.In this approach,a RLC peaking network,also called resistance-inductance-capacitance（RLC） loss compensation network,is placed at the base of a common-base transistor,instead of a DC blocking capacitor in the conventional cascode structure.According to previous research,different working conditions of the transistors in the cascode structure will lead to a noticeable influence on the linearity of the whole power amplifier.However,in addition to broad bandwidth,the linearity is another key figure-of-merit for a high quality system.The paper presents a method to improve both bandwidth and linearity of a cascode broadband power amplifier.The optimization can be accomplished by adjusting the values of the components of the RLC peaking compensation network to make the active devices work in the maximum linear dynamic range.As a result,both of an improvement in the linearity and high power added efficiency can be achieved.This paper presents the optimization principles of the components＇ values of the RLC peaking compensation network,and explains the reason why a higher linearity is achieved without degradation of power added efficiency.Moreover,a numerical analysis of the 3rd order intercept point（IP3） based on Volterra Series method demonstrates that the IP3 could be improved by about 3 dB using this optimized components＇ values of RLC peaking compensation network.Finally two cascode power amplifiers,which are with the RLC peaking compensa

关 键 词：补偿网络 Cascode放大器 线性度 VOLTERRA SERIES 

分 类 号：TN948.53[电子电信—信号与信息处理]